A redundant power system, which includes a redundant power source, monitors remote power sources to detect when any of the remote power sources requires take-over by the redundant power system before the operation of the loads of the remote power sources may be affected. If any of the remote power sources are failing because of a catastrophic failure, such as a shorted load, then engaging the redundant power system may cause the redundant power source to overload and fail. If the redundant power source is supplying power to other remote power sources at the same time, then all of the remote power sources in the system may have their operation interrupted.
A number of prior solutions to the problem of supplying redundant power to failing remote power sources exist. In one prior solution, the redundant power source is engaged as soon as the remote power source begins to fail and then, if the redundant power source experiences a drop in voltage or excess current draw, then an attempt is made to withdraw the redundant power source as quickly as possible. This solution can be risky because the time allowed to detect the abnormal event, and to disengage to the redundant power source, can be very short and once the redundant power source is stressed, the redundant power source may require an extended period of time to recover. This extended recovery period can interrupt the operation of the system even after the abnormal, failed load is removed.
In another prior solution, the redundant power source may be slowly engaged such that any abnormal condition may be detected before the redundant power source experiences excess stress. There are several drawbacks to this prior solution. One drawback is that it takes longer to fully take over for the remote power source and, therefore, it is difficult to guarantee that the remote power source's operation is not interrupted (e.g., voltage becomes too low). A second drawback involves the cost of this solution. A circuit that can slowly feed power in increasing and precise amounts is more complicated and, therefore, more expensive, and additionally requires an accurate/sensitive measuring capability in order to detect any abnormal current draw. A third drawback is that high power may be dissipated in this type of circuit when it is not fully engaged. Dissipation of this extra power can be expensive and may increase the size of the circuit.